Little Apple Trees - grafted on M27, the most dwarfing rootstock
Several years ago my wife passed on the following request from her best friend: ‘Janet wants some ‘little trees’’? After some discussion, I gathered that she would like to have trees that grew no more than five to six feet tall and did not become too spreading.
This gave me the opportunity to try out the much-maligned M27 rootstock. For anyone not familiar with the Malling rootstock system, M27 is the most dwarfing rootstock. It is not recommended by amateur gardeners, commercial apple growers or nurserymen; they say it is difficult to grow well and the resulting trees can be a disappointment. I faced the challenge of growing apples, grafted onto M27 rootstock, in a lawn and in heavy clay soil.
The four trees, Saturn, Winter Gem, Limelight and Red Devil were to be grown in my favourite restricted form, that is, as dwarf pyramids. My instructions to Janet and her family were to dig out a hole for each tree, around three feet across and as deep as their energies would take them. They were to throw away all the spoil and back-fill the hole with a 3:2:1 mix of top-soil, peat and sharp sand. How closely they followed my guide lines is uncertain, but four apples and two pear trees were planted in the lawn, with a stake for each one; trees on M27 rootstock need a permanent stake. I pruned them back to around twenty inches and took off most of the ‘feathers’ (small lateral branches); any remaining laterals were pruned back hard. A sprinkling of Growmore was given in the early spring. I left instructions to mulch with grass cuttings in late spring and to water periodically through to September.
In year two, I pruned the trees in the winter and I also remember the sighs and groans in the spring as I pinched out the blossom. I think they were so disappointed that this was the reason I was not invited back again.
Several years later I was asked to look at the broken branches on these trees. This was a direct result of the lack of formative pruning and over cropping, but the trees had cropped and magnificently, which I put down to the precocity of the rootstock, the initial good husbandry, a friable planting medium which got the roots away and ongoing watering through the growing season. I think that M27 rootstocks have a bad name because people plant them, walk away from them and leave the trees to get on with it; they forget to look after them.
As can be seen from the pictures, the trees were a success. Most of them had cropped heavily the previous year and some fruit had already been picked from these trees. They would have been even more productive with additional formative pruning and year on year summer pruning, so as to create a compact tree with more fruit buds.
Around the time, that my wife’s friend planted the fruit trees in her lawn, I also had grafted for my own garden two vigorous varieties on M27 rootstock; these being Blenheim Orange (a triploid) and Winter Gem. It is quite evident that triploids and more vigorous diploid varieties require the next rootstock down, if not two rootstocks down from the one you might use for a diploid: that is graft on M27 rather than M26 or M9. My theory on skin colour is that the harder you work or handicap the tree the better the colour. A dwarfing rootstock effectively makes the variety grafted on to it work harder; you are giving it more to do, due to the restriction on vigour. A vigorous variety produces lots of lush growth and little fruit or fruit of poor colour.
John Scott, the founder of Scott’s nursery said ‘fruit not faggots’ and that is as true today, as it was in the nineteenth century. This is what I set out to prove by trialling the vigorous Blenheim Orange and Winter Gem on M27 rootstocks. My Blenheim Orange on M26 rootstock seldom has good colour, definitely not living up to its name. Last year the fruit from the tree grafted on M27 rootstock was nicely coloured, but most of the fruit from the M26 tree was green. The same went for the Winter Gem, which showed poor skin colour on M26 rootstock and a good flush on M27. So exasperated am I by the poor quality fruit of the M26 Blenheim and Winter Gem that they are both coming out.
My recommendation is to ignore the bad press and give both diploid and triploid varieties a try on M27 rootstocks: plant some in the lawn or flower beds and give them plenty of care.
This article was first published in the newsletter of the Royal Horticultural Society Fruit Group; reproduced here with permission.
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